U.S. patent number 4,270,360 [Application Number 06/116,481] was granted by the patent office on 1981-06-02 for device for storage of hydrogen.
This patent grant is currently assigned to Agency of Industrial Science & Technology, Ministry of International Trade & Industry. Invention is credited to Aakihiko Kato, Masanori Nakane, Yasuaki Osumi, Hiroshi Suzuki.
United States Patent |
4,270,360 |
Nakane , et al. |
June 2, 1981 |
Device for storage of hydrogen
Abstract
A device for the storage of hydrogen, comprising a container,
two porous plates opposed parallelly to each other across a fixed
distance and fastened to the inner wall of the container,
heating/cooling members disposed one each outside the porous plates
and separated by a fixed distance from the corresponding porous
plates, and an alloy capable of storing hydrogen placed in the
spaces formed between the porous plates and the heating/cooling
members.
Inventors: |
Nakane; Masanori (Takatsuki,
JP), Osumi; Yasuaki (Minoo, JP), Suzuki;
Hiroshi (Ikeda, JP), Kato; Aakihiko (Matsubara,
JP) |
Assignee: |
Agency of Industrial Science &
Technology (Tokyo, JP)
Ministry of International Trade & Industry (Tokyo,
JP)
|
Family
ID: |
12372847 |
Appl.
No.: |
06/116,481 |
Filed: |
January 29, 1980 |
Foreign Application Priority Data
|
|
|
|
|
Mar 19, 1979 [JP] |
|
|
54/32937 |
|
Current U.S.
Class: |
62/46.2; 165/61;
206/.7; 123/DIG.12; 165/104.12 |
Current CPC
Class: |
C01B
3/0068 (20130101); C01B 3/0057 (20130101); F17C
11/00 (20130101); C01B 3/0031 (20130101); C01B
3/0084 (20130101); C01B 3/0005 (20130101); Y02E
60/321 (20130101); Y10S 123/12 (20130101); Y02P
90/45 (20151101); Y02E 60/32 (20130101); Y02E
60/327 (20130101) |
Current International
Class: |
F17C
11/00 (20060101); C01B 3/00 (20060101); F17C
011/00 () |
Field of
Search: |
;62/48 ;423/248 ;34/15
;123/DIG.12 ;165/61,DIG.17 ;206/.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
5090512 |
|
Feb 1977 |
|
JP |
|
2030693 |
|
Oct 1980 |
|
GB |
|
Primary Examiner: Capossela; Ronald C.
Attorney, Agent or Firm: Kelman; Kurt
Claims
What is claimed is:
1. A device for the storage of hydrogen, which comprises:
a container,
two porous plates opposed parallelly to each other across a fixed
distance within the container and fastened to the inner wall of the
container so as to divide the interior of the container,
two heating/cooling members disposed one each outside the porous
plates and separated from the corresponding porous plates by a
fixed distance, and
an alloy capable of storing hydrogen placed in the spaces
intervening between the porous plates and the heating/cooling
members.
2. The device according to claim 1, wherein the heating/cooling
members are each provided with an inner space for retaining a
heating/cooling medium and the inner spaces communicate with each
other via a connecting pipe.
3. The device according to claim 1, wherein the space intervening
between the two porous plates is provided in the container wall
with a hydrogen discharge pipe.
4. A device for the storage of hydrogen, which comprises:
a container,
at least three heating/cooling members spaced regularly from each
other and arranged parallelly to each other within the container so
as to divide the interior of the container,
two porous plates opposed parallelly to each other across a fixed
distance within each of the spaces intervening between the adjacent
heating/cooling members, and
an alloy capable of storing hydrogen placed in the spaces
intervening between the porous plates and the heating/cooling
members.
5. The device according to claim 4, wherein the heating/cooling
members are each provided with an inner space for retaining
heating/cooling medium and the inner spaces communicate with each
other via a connecting pipe.
6. The device according to claim 4, wherein the space intervening
between the two porous plates is provided in the container wall
with a hydrogen discharge pipe.
Description
BACKGROUND OF THE INVENTION
This invention relates to a device for the storage of hydrogen by
use of an alloy capable of storing hydrogen therein.
Hydrogen, as an energy source which promises to take the place of
fossil fuels such petroleum and coal which are destined to be
exhausted sooner or later, has been attracting increasing
attention.
Methods proposed to date for the storage of hydrogen include (A) a
method for storing hydrogen in its gaseous form, (B) a method for
storing hydrogen in its liquefied form, and (C) a method for
storing hydrogen as metal hydride by use of an alloy.
The method (A), because of the necessity for handling hydrogen
under a very high pressure exceeding 150 atmospheres, cannot
necessarily be called an efficient approach and, to make the matter
worse, proves deficient in safety. The method (B) has the
disadvantage that the production of liquefied hydrogen requires
supply of hydrogen of extremely high purity, installation of
expensive manufacturing facilities and provision of storage
containers capable of withstanding very low temperatures. Thus,
this method has found utility in only limited applications.
The method (C) makes use of the ability of a certain metal or alloy
to occlude hydrogen and convert itself into a metal hydride and the
ability of this metal hydride to release the hydrogen and convert
itself back to its original metal or alloy. It enjoys better
practical utility than the methods (A) and (B). Research has been
positively pursued in search of alloys which are optimum for the
storage of hydrogen by occlusion. On the other hand, almost no
consideration has been given to the development of a device for
storage of hydrogen by use of such an alloy. The development of
such a device has been generally ignored because of a very great
difficulty which soon becomes obvious to anyone who begins
developmental work. Alloys for storing hydrogen evolve heat during
the occlusion of hydrogen and absorb heat during the release of
hydrogen. This means that the storage device must be of a structure
which allows the evolution and absorption of heat to proceed
smoothly. To devise a device of a structure which permits smooth
evolution and absorption of heat is a very difficult task.
The inventors therefore continued a diligent study in search of a
device with a construction which is free from the aforementioned
problem of heat conduction involved during the occlusion and
release of hydrogen by the alloy and capable of retaining, in
principle, the optimum charge amount of the alloy for the storage
of hydrogen. The present invention has resulted from this
study.
The object of this invention is to provide a device for the storage
of hydrogen by use of an alloy capable of occluding hydrogen, which
device eliminates the problem of heat conduction involved during
the occlusion and release of hydrogen by the alloy, enjoys high
operational efficiency and economy, has high safety, and permits
ready scaling up of the equipment for large applications.
SUMMARY OF THE INVENTION
To accomplish the object described above according to the present
invention, there is provided a device for the storage of hydrogen,
which device comprises a closed container, two porous plates
opposed parallelly to each other across a fixed distance and
fastened to the interior wall of the closed container so as to
divide the interior space of the container, and two heating/cooling
members disposed one each outside the porous plates and separated
by a fixed distance from the corresponding porous plates, with
spaces between the porous plates and the corresponding
heating/cooling members filled with such an amount of the
hydrogen-storage alloy as to optimize the conduction of the heat
being evolved and absorbed by the alloy during the occlusion and
release of hydrogen.
In short, the device for the storage of hydrogen according to this
invention is characterized by being packed with the
hydrogen-storage alloy and further being provided with two
heating/cooling members which are disposed one each outside the
packed alloy. To be specific, the alloy and the heating/cooling
members are adapted relative to each other so that, when the
heating/cooling members are heated or cooled for the release or
occlusion of hydrogen by the alloy, the transfer of heat or the
conduction of heat between the alloy and the heating/cooling
members will be retained under a fixed relationship. The
aforementioned combination of the component parts of the device
forms one basic unit. The device can be scaled up, therefore, by
increasing the number of such basic units. This permits the total
capacity of the device for the storage of hydrogen to be easily
increased without entailing any change to the internal conditions
of the device.
BRIEF EXPLANATION OF THE DRAWING
FIG. 1 represents one preferred embodiment of the device for the
storage of hydrogen according to the present invention.
FIG. 2 is a partially cutaway perspective view of the device of
FIG. 1.
FIG. 3 represents a typical device for the storage of hydrogen
according to this invention, which device is formed by having a
plurality of basic units of the construction of FIG. 1 parallelly
arranged.
FIG. 4 is a partially cutaway perspective view of the device of
FIG. 3.
FIG. 5 is another preferred embodiment of the device for the
storage of hydrogen according to this invention, having a plurality
of basic units of the construction of FIG. 1 parallelly
arranged.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The alloy for the storage of hydrogen which is used in the device
according to this invention is a binary, ternary or quaternary
alloy generally using magnesium, titanium or a rare earth metal as
its principal component. Examples of alloys usable for this purpose
include Mg.sub.2 Ni, TiFe, TiCo.sub.0.5 Fe.sub.0.5, TiCo.sub.0.5
Mn.sub.0.5, LaNi.sub.5, MmNi.sub.5, MmNi.sub.4.5 Al.sub.0.5,
MmNi.sub.4.5 Mn.sub.0.5 and MmNi.sub.2.5 Co.sub.2.5.
The alloy occludes hydrogen at the optimum temperature under the
optimum hydrogen pressure according to the hydrogen
occlusion-release characteristics peculiar to that alloy to form
its hydride. This hydride of the alloy undergoes thermal
decomposition with release of hydrogen at appropriate temperature
and pressure.
Generally, the porous plates are unglazed ceramic plates, sintered
metal plates or metal gauzes. Of these plates, sintered metal
plates are used preferably. One essential property required for the
porous plates is mechanical strength sufficient to withstand the
pressure exerted by the hydrogen-storage alloy which is placed in
the device. For the sake of the compactness of the device, these
porous plates are desired to have the least allowable thickness,
which generally falls in the range of from 1 to 5 mm. In the case
of sintered metal plates or metal gauzes, the metal used as their
material is only required to be inactive to hydrogen. Stainless
steel, aluminum, nickel, etc. prove to be most suitable as the
material for sintered plates because of their outstanding
fabricability.
Now, one embodiment of the device for the storage of hydrogen
according to the present invention will be described with reference
to the accompanying drawing.
It should be noted that this invention is not limited by the
embodiments to be cited hereinafter but may be freely modified
within the scope of the technical idea underlying this
invention.
FIG. 1 is a schematic sectioned view of one embodiment of the
device for the storage of hydrogen according to this invention, and
FIG. 2 is a partially cutaway perspective view of the device of
FIG. 1. In the accompanying drawing, the device for the storage of
hydrogen according to this invention is illustrated as possessing
the appearance of a drum or a cylinder of small height. The
apparatus is not necessarily limited to this shape. It may have any
suitably selected shape. For example, a container of a rectangular
or elliptic cross section may be advantageously utilized. It is a
closed container because it must fulfill the basic requirement of
keeping hydrogen entrapped therein. The container is also required
to withstand pressure to some extent.
At the center of the interior of this container, two sintered metal
plates 1, 2 are parallelly opposed to each other across a fixed
distance and fastened to the inner wall of the container. The term
"sintered metal plates" shall be used herein as representing porous
plates.
The sintered metal plates 1, 2 and the heating/cooling members 5, 6
are required to be separated from each other so much as to give
rise to spaces large enough for holding therein ample supply of
hydrogen-storage alloy. The each heating/cooling members disposed
one each outside the two sintered metal plates are desired to have
an equal capacity for heating and cooling. In due consideration of
these requirements, it is desirable for the sintered metal plates
to be located about halfway along the entire thickness of the
"drum" as illustrated in FIG. 2.
The sintered metal plates have the shape of circular plates in FIG.
2. They are not always limited to this shape. Optionally they may
be square plates or rectangular plates, according to the shape of
the container being used. The space between the two parallel
sintered metal plates serves as the passage for hydrogen which is
occluded or released by the alloy. The distance between the two
sintered metal plates is to be determined by the velocities of the
inflow and outflow of hydrogen during the occlusion and release of
hydrogen by the alloy, the total amount of the alloy to be placed
in the device and other characteristics of the alloy. Generally,
this distance is desired to fall within the range of from 5 to 20
mm, preferably from 8 to 10 mm. The space between the two sintered
metal plates connects with a valve 3 adapted to control the supply
and discharge of hydrogen. The valve 3 connects to hydrogen feed
pipe 4. The hydrogen feed pipe 4 functions as a path for
discharging the hydrogen released by the alloy.
Outside the opposed sintered metal plates, the heating/cooling
members 5, 6 each embracing an inner space for retaining a heating
or cooling medium are disposed at a fixed distance (to be described
afterward) from the corresponding sintered metal plates. These
members are adapted to communicate with each other via a connection
pipe 7. The heating/cooling member 5 is provided with an inlet pipe
8 and the heating/cooling member 6 with an outlet pipe 9. A cooling
medium is introduced through the inlet pipe 8 while the
hydrogen-storage alloy is occluding hydrogen, and a heating medium
is supplied through this pipe while the alloy is releasing
hydrogen. For the purpose of heating and cooling, gaseous or liquid
media may be used. These media need not be prepared specifically
for use in the operation of the device of this invention. As the
heating medium, an effluent liquid or exhaust gas of varying
temperature (of not more than 100.degree. C.) may be used. As the
cooling medium, waste water or plain air of room temperature or a
lower temperature may be used. The temperatures of the heating and
cooling media which are to be actually used are determined by the
characteristics of hydrogen occlusion and release exhibited by the
hydrogen-storage alloy. The spaces 10 and 11 which occur between
the sintered metal plate 1 and the heating/cooling member 5 and
between the sintered metal plate 2 and the heating/cooling member 6
are each filled with the hydrogen-storage alloy which is generally
in the form of powder or granules.
Generally, the thermal conductivity which the hydrogen-storage
alloy exhibits before occlusion of hydrogen and that the alloy
exhibits after occlusion of hydrogen differ widely. Thus, the
thickness of the packed hydrogen-storage alloy formed in the spaces
10, 11 governs the efficiency of the device for the storage of
hydrogen. The heat conduction increases with the decreasing
thickness of the packed alloy. If this thickness is too small,
however, the compactness of the device is spoiled.
The thickness of the packed hydrogen-storage alloy is determined by
the kind of the particular hydrogen-storage alloy to be used,
namely the thermal conductivity of the alloy. When LaNi.sub.5 is
adopted as the alloy, for example, the thickness of the packed
alloy to be placed in the space between the sintered metal plate
and the heating/cooling member is desired to be about 2 cm.
To uniformize the conditions for the occlusion and release of
hydrogen, namely the conditions of heat conduction, at various
portions of the packed hydrogen-storage alloy placed in the space
between the sintered metal plate 1 and the surface 12 of the
heating/cooling member 5, the sintered metal plate 1 and the
surface 12 of the corresponding heating/cooling member 5 are
generally desired to be kept parallel to each other. More
desirably, the two opposed surfaces should be parallel to each
other and identical in shape.
When the device for the storage of hydrogen of this invention
illustrated in FIGS. 1-2 is assumed to use LaNi.sub.5 as the
hydrogen-storage alloy and store 1.6 Nm.sup.3 of hydrogen, typical
physical particulars for this device may be as follows. Since the
hydride of LaNi.sub.5 is LaNi.sub.5 H.sub.6, the weight of
LaNi.sub.5 required to occlude 1.6 Nm.sup.3 of hydrogen is 10.3 kg.
Since the specific gravity of LaNi.sub.5 is 8.4 and the packing
ratio of LaNi.sub.5 is 75%, the volume of the space to be filled
with LaNi.sub.5 is 1.63 liters. When the thickness of the packed
bed of LaNi.sub.5 is fixed at the optimum value of 2 cm as
described above, the bottom area of the drum illustrated in FIG. 2
is 407.5 cm.sup.2 and the diameter of this circle is 22.8 cm. Since
the packed alloys have a total thickness of 2 cm.times.2, the
porous plates a total thickness of 1 cm, and the heating/cooling
members a total thickness of 1.5 cm.times.2, therefore, the total
thickness of the device (drum) is 8 cm. The device, therefore, has
a size of 22.8 cm (diameter).times.8 cm (thickness).
Now, the procedure of the operations of occlusion and release of
hydrogen by the device of this invention as illustrated in FIGS.
1-2 will be described.
First, the hydrogen-storage alloy placed in the device is
activated. A typical method of activation will be described. The
alloy is caused to occlude hydrogen under a hydrogen pressure of 7
kg/cm.sup.2. Then the hydrogen occluding alloy is caused to release
hydrogen at a temperature of 70.degree. C. This treatment serves
the purpose of activating the hydrogen-storage alloy.
Then, the cooling medium is passed through the inlet pipe 8 to cool
the device and, at the same time, the hydrogen from a cylinder is
fed under pressure through the hydrogen feed pipe 4 into the
device. The pressure under which the hydrogen is introduced into
the device has an effect upon the velocity of the occlusion of
hydrogen by the hydrogen-storage alloy. During the introduction of
hydrogen to the device, therefore, the pressure is controlled by
adjusting the valve 3. Generally, the pressure for the introduction
of hydrogen into the device is not less than the pressure of
equilibrium dissociation of the hydrogen-storage alloy at arbitrary
temperature and not more than the maximum pressure which can be
endured by the container of the device.
The hydrogen which has been introduced under pressure into the
space between the two sintered metal plates as described above
uniformly passes into the whole of the packed hydrogen-storage
alloy. The occlusion of hydrogen proceeds uniformly and reaches its
completion after a certain period of time.
When the hydrogen stored as described above in the alloy is to be
used, the cooling medium is switched to the heating medium to heat
the packed hydrogen-storage alloy and cause the metal hydride to
release hydrogen. The hydrogen thus released from the metal hydride
travels through the sintered metal plates in the direction opposite
the direction of travel during the occlusion. At a flow rate which
is controlled by the valve 3, the hydrogen is discharged through
the hydrogen feed pipe 4.
In the device for the storage of hydrogen according to this
invention which is constructed as described above, the optimum
thickness of the packed hydrogen-storage alloy which is determined
by the hydrogen occlusion-release characteristics of the alloy is
retained.
Since the condition of the heat conduction to the packed
hydrogen-storage alloy during the heating or cooling is retained
constant at all the stages of occlusion and release of hydrogen and
at all the portions of the alloy, the occlusion and release of
hydrogen by the alloy within this device can be continued
smoothly.
The device of this invention can be scaled up to a desired capacity
by simply serially arranging as many basic units of the
aforementioned construction as required on the particular
occasion.
In the combination of a multiplicity of basic units, a compact
device wherein the heating/cooling members are disposed so that
each of the members intervenes between a pair of porous plates and
serves for both the two packed hydrogen-storage alloys placed in
the two spaces formed one each on the opposite sides of the member
between the opposed surfaces of the pair of porous plates can be
constructed as follows. Specifically, this compact device is
obtained by having at least three heating/cooling members
parallelly spaced so as to divide the interior of the pressureproof
closed container, having two porous plates parallelly opposed to
each other in each of the spaces intervening between the adjacent
heating/cooling members and allowing the spaces intervening between
the porous plates and the heating/cooling members to be packed with
such an amount of the hydrogen-storage alloy as will best suit the
heat conduction involved in the occlusion and release of hydrogen
by the alloy. In the device formed by the combination of the
multiplicity of basic units, the thickness of the packed
hydrogen-storage alloy placed in each of the multiplicity of spaces
is not changed at all by scaling up the capacity of the device.
Thus, the optimum conditions of heat conduction are retained
intact. This means that there is absolutely no need of paying any
consideration to the possibility of a change in the conditions of
heat conduction in the interior of the packed bed of the
hydrogen-storage alloy as suffered by the conventional device in
consequence of scaling up capacity. The hydrogen-storage device of
such a large capacity obtained by the present invention, therefore,
enjoys as high operational efficiency, economy and safety as the
device of the size of the basic unit.
Now, a few typical scaled up basic units of the device for the
storage of hydrogen according to the present invention will be
described below.
FIG. 3 is a sectioned view of the device for the storage of
hydrogen which is formed by having serially arranged a plurality of
basic units of the device of this invention shown in FIG. 1 and
covering the combined basic units with an angular container whose
corners fall on the inner wall of a cylindrical container. FIG. 4
is a partially cutaway perspective view of the device.
As is plain from FIG. 3, two sintered metal plates 1, 2 and two
heating/cooling members 5, 6 which are parallelly arranged form
each of the plurality of small compartments, and the spaces
intervening between the adjacent sintered metal plates and
heating/cooling members are each packed with the hydrogen-storage
alloy having a thickness which permits retention of the optimum
heat-exchange efficiency.
When LaNi.sub.5 is used as the hydrogen-storage alloy, since the
optimum thickness of the packed bed of this alloy is about 2 cm as
already described, the device of FIG. 3 used for the storage of 16
Nm.sup.3 of hydrogen satisfies the following physical
particulars.
______________________________________ Weight of LaNi.sub.5 103 kg
Specific gravity of LaNi.sub.5 8.4 Void ratio 34.7% Packing ratio
of alloy 75% Thickness of packed bed of alloy 2 cm Number of packed
bed of alloy 16 Thickness of porous plate 1 cm Number of porous
plate 8 Thickness of heating/cooling member 1.5 cm Number of
heating/cooling member 9 Thickness of device (2 cm .times. 16 + 1
cm .times. 8 + 1.5 cm .times. 9) 53.5 cm Space for fitting the
device 2.5 cm ______________________________________
In view of these dimensions, a cylindrical container having an
inner diameter of 79.2 cm may be used. The thickness of the
cylindrical container is 10 cm, for example.
The device, therefore, has the following size: 79.2 cm
(diameter).times.10 cm (thickness).
The procedure for the operation of this device is entirely the same
as that involved in the device illustrated in FIG. 1 and FIG.
2.
Also in the scaled up device of the construction illustrated in
FIGS. 3-4, the optimum thickness of the packed bed of the
hydrogen-storage alloy used in the device of FIG. 1 is retained.
This enlarged device, therefore, similarly attains the
aforementioned effect contemplated by this invention while
permitting a desired increase to the capacity for the storage of
hydrogen.
The devices for the storage of hydrogen illustrated in FIG. 1 and
FIG. 3 and the conventional cylinder used for the storage of
hydrogen are compared in terms of capacity for storage in Table 1
below.
TABLE 1 ______________________________________ Capacity for Volume
Pressure storage of Storage device (liters) (atm) hydrogen
(Nm.sup.3) ______________________________________ Conventional
cylinder 57 150 7 Device of FIG. 1 3.5 9.7 max. 1.6 Device of FIG.
3 49.2 9.7 max. 16 ______________________________________
It is noted from the data that for the storage of a fixed volume of
hydrogen, the device of this invention using LaNi.sub.5 as the
hydrogen-storage alloy requires only 1/3 to 1/4 of the volume
required by the conventional cylinder and that the pressure
required at the time of storage is markedly decreased. Thus, the
device of this invention provides required storage of hydrogen with
much higher efficiency.
FIG. 5 depicts a concept of the device constructed by having a
still greater number of basic units of the construction of FIG. 1
arranged serially. In this device, hydrogen is fed through the feed
pipe 4 and allowed to be occluded by the hydrogen-storage alloy
placed in the individual compartments 10, 11. The heating (cooling)
medium is fed through the inlet pipe 8. (For the simplicity of
drawing, the sintered metal plates 1, 2 are represented by one
line.)
Besides the parallel arrangement, the plurality of basic units used
for the purpose of scaling up capacity may be arranged in serial
connection. Optionally, groups each having a plurality of basic
units arranged parallelly may be arranged in serial connection.
Another combination wherein a plurality of basic units are arranged
one on top of another in a vertical direction enjoys the advantage
of economizing the floor space required for the installation.
In any event, the characteristics of the basic unit of the device
of this invention are retained intact even when the device is
scaled up in capacity. That is to say, scaling up permits a desired
increase of the capacity of the device for the storage of hydrogen
without sacrificing the effect of the invention.
Now, this invention will be described below with reference to a
working example.
EXAMPLE
In a device of the construction of FIG. 1, porous plates 1, 2 were
separated from each other by 10 mm, the porous plates 1, 2 were
separated respectively from heating/cooling members 5, 6 by a fixed
distance of 20 mm, the heating/cooling members each had an inner
volume of 408 cm.sup.3 and a thickness of 15 mm, and the container
as the outer shell of the device had a diameter of 22.8 cm. In this
device 10.3 kg of LaNi.sub.5 as the hydrogen-storage alloy was
placed in the spaces 10, 11. The porous plates were sintered plates
of stainless steel 2 mm in thickness.
Hydrogen of a pressure of 7 kg/cm.sup.2 was introduced into the
device at room temperature to be occluded by the alloy.
Subsequently, the alloy was heated to 70.degree. C. to release
hydrogen. The alloy was fully activated by repeating the procedure.
After the activation, a cooling medium was introduced through an
inlet pipe 8 into the heating/cooling members 5, 6 to cool the
alloy to 5.degree. C. At the same time, hydrogen was introduced
under a pressure of 7 kg/cm.sup.2 into the porous plates. After 120
minutes of this supply of hydrogen, the alloy was converted into a
hydride by occlusion of a total of 143 g (1.6 Nm.sup.3) of
hydrogen. Then, instead of the cooling medium, a heating medium was
introduced through the inlet pipes 8 to heat the alloy to about
80.degree. C. In 120 minutes, the hydride completely released the
hydrogen.
* * * * *